A variety of devices are used in the medical/dental field having multiple elements which are spatially adjustable relative to one another. A number of techniques and mechanisms have been used to effect these adjustments. By way of example, orthodontic head gears or face bows utilize such a technique to apply a correcting force to a patient's teeth. A face bow typically includes an outer bow fixed to an inner bow. The outer bow has two ends and an elastic element is looped around the back of the patient's neck and hooked onto the ends of the outer bow in order to supply a hold-down force to particular teeth of the patient through the inner bow. The inner bow typically has tubular ends, each of which telescopically receive a face bow wire, with the wire fixed thereto. The inner bow is usually placed in the patient's mouth at about the level of the canine teeth. The protruding end of each face bow wire is attached, at the rear of the mouth, to whichever molar is to be moved by inserting the wire end into a small buccal tube which has been attached to the molar by means of a band. In this manner, the wire can apply a rearward corrective force to the molar by limiting relative movement between each of the wires and the inner face bow. The end of the wire is free to slide axially inside the tube. Therefore, limitation of this relative movement is achieved by making a loop in each of the face bow wires which cannot slip through the respective buccal tubes. Each loop thus serves as a stop enabling the corrective force to be applied. The wire can also be bent to place the free end of the loop at a desired angle to the fixed end of the wire in order to change how the corrective force is applied to the molar (i.e., to achieve the desired movement of the tooth.
At intermediate visits, the orthodontist previously had to regularly bend the loop in order to make corrections to the force being applied. In particular, the bow length is increased or decreased by curving the loop more or less. A number of such bending procedures, in many cases, results in breakage of the wire near the loop due to fatigue of the wire material. While such failures result in additional work and costs, it also is dangerous and potentially detrimental to the patient's health, for example, a piece of wire may break off and end up in the patient's throat. The presence of the loops inside of the patient's mouth has also been found to be unpleasant for some patients. Thus, there is a need for a different technique or mechanism for adjusting each of the face bow wires relative to the inner face bow that avoids having to repeatedly deform the wires and eliminate the need for the loops.
With many of these devices, the first and second elements are telescopically engaged with each other. With one such device, a Herbst appliance, one element includes a pin and the other element includes a tube. One end of the pin is slidably received by one end of the tube. Two pin/tube combinations are used, one on either side of the patient's mouth to make corrections in the relative position of the patient's upper and lower mandible. On each side of the patient's mouth, the other end of the pin is mounted to a patient's tooth on the lower mandible and the other end of the tube is mounted to a tooth on the upper mandible. Relative telescopic movement between each pin and tube is limited by inserting a stop, such as a shorter length of smaller diameter tube, into the tubular element. It is often desirable to adjust how deep one or both of the pins can slide into their respective tubes. To accomplish this adjustment, it is often necessary to remove one or both of the Herbst elements from the patient's mouth before the changes can be made. Having to remove one or both of the Herbst elements from the patient's mouth tends to prolong the treatment period. In addition, even once removed, the prior Herbst elements are not readily adjustable. Other adjustable telescoping devices in the medical/dental field suffer from similar problems. Therefore, there is a need for a device or system which can avoid these problems.
Another example of such devices includes scoliosis correction systems for stabilizing the patient's spine. Such systems often include sets of dual spinal hooks for attachment to the patient's vertebra. Each set of hooks is mounted to a stabilization or correction bar positioned along the patient's spine. Threaded bolts or screws have been used to adjust the hooks relative to one another in each set. In addition, set screws have been used to fix the location of each set of hooks along the stabilization bar. However, the threads of these bolts and screws have a tendency to strip or gall and their installation can be cumbersome because there is not much room to use the tools necessary to adjust these screws and bolts. In addition, the screws have been known to have a tendency to back-out in in-vivo situations. This could cause the device to loosen, requiring additional surgery.
A number of medical/dental devices are fastened directly into a patient's bone structure. For example, Osteogenesis distraction devices typically include at least one mounting plate with one or more holes formed therethrough for receiving a fastener, like a screw, which is anchored into the patient's bone. It has been found that with time the screw has a tendency to back out of the plate hole. Therefore, there is also a need to limit movement of the screw, once inserted into the patient's bone, relative to the mounting plate.